Aircraft structures commonly comprise a number of doors such as passenger doors, cargo hold doors, maintenance door (or hatches) and landing gear doors. Such doors provide access to the internal parts of the aircraft when open and close so as to conform to the surrounding aircraft structure. An important aspect of many such doors is that during their opening procedure and in their open position they do not impinge, catch or otherwise undesirably contact other parts of the aircraft structure. Furthermore, when the aircraft in on the ground, the doors should not impinge on the ground or other ancillary structures such as loading ramps or gantries. For example, landing gear doors must provide clearance to the ground, the landing gear, and any symmetrically opposite landing gear door under all operating conditions of the aircraft.
A problem arises when a door is large and the distance available to clear other aircraft structures or other external structures is relatively small. For example, if the door is a landing gear door, the ground clearances may be small and the door may be liable to be damaged by contact with the ground. One solution is to provide a two-part door which folds up to provide the necessary clearance. Such doors, when provided for landing gear, commonly fold inwards towards the landing gear and can require additional devices to ensure that extension of the landing gear is achieved without interference between the landing gear and the door. Furthermore, the folding procedure and mechanism for a folding door can be complex.